Polyvinylidene fluoride/poly(ethylene terephthalate) conductive composites for proton exchange membrane fuel cell bipolar plates: Crystallization, structure, and through‐plane electrical resistivity

Abstract

AbstractPolyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET)‐based composites for proton exchange membrane fuel cell bipolar plates (BPs) were prepared at different crystallization temperatures and characterized by X‐ray diffraction, differential scanning calorimetry, and resistivity setup. Composite conductivity was made possible by using a mixture of carbon black (CB) and graphite (GR). To improve composite processability, its viscosity was reduced by adding a small amount of cyclic butylene terephthalate (c‐BT) oligomer and thermoplastic polyolefin elastomer. In the PVDF/PET‐based composite, it was found that PVDF phase could crystallize easily but PET crystallization was difficult. Because of the CB/GR additives, the formed crystals in PVDF/PET phases had a poor perfection degree and showed a lower melting temperature when compared with pure PVDF and PET. It was observed that PET nucleation was accelerated but not that of PVDF. According to through‐plane resistivity results, composite crystallization temperature range was divided into two parts (below/above 170°C), in which a different variation behavior of through‐plane resistivity was observed. It has been proved that the resistivity was mainly governed by the network of CB/GR developed inside the PET phase, and decreasing the crystallinity of PET led to a decrease of through‐plane resistivity, which is desirable for BPs. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers